1. Field of the Invention
The present invention relates to an image drawing apparatus and method.
2. Related Background Art
Recently, images in medical fields are often taken on X-ray films via high speed digital interface in place of video interface. Such images include CT (computer tomograph) images, NMR (nuclear magnetic resonance) images, and DSA (digital subtraction angiography) images. Image drawing apparatuses (imagers) for such purposes are typically laser imagers.
The reason why laser imagers are widely used is as follows. Conventional video interface is convenient on one hand in that CRT monitor display video signals for medical CT, NMR, DSA, and the like are directly supplied to a medical purpose laser imager. On the other hand, there is a disadvantage that noises may enter while digital data generated by medical CT, NMR, DSA, and the like is once converted into analog video signals and then again converted into digital signals by a medical purpose laser imager. Particularly for DSA, its image size is large and its video signal clock rate is as very fast as 50 MHz or so, so that it is difficult to design an interface circuit.
From the above reason, without using conventional video interface, various types of recent modalities (medical image generating apparatus) directly output digital images.
Also in the field of OA machines, imagers capable of printing digital images on printing sheets of various sizes such as A4 and B4 are used, which are generally called laser printers.
From the viewpoint of computer interconnections, digital interconnections via networks have been established. In the medical fields, a communication protocol called DICOM (Digital Imaging and Communications in Medicine) which is an object-oriented protocol, and other protocols have also been established. Images having different attributes are now printed on various types of films which users desire.
To meet such various needs, object-oriented laser imagers are now gradually prevailing because communication control is easy and integrity is good.
Conventional printing by using a conventional object-oriented laser imager will be described.
As shown in FIG. 19, in object-oriented printing, each client of modalities such as CT 501, NMR 502, and DSA 503, and work stations on a network 506 requests a laser imager 504 to construct an object of a film session which is a set of a plurality of films, objects of a plurality of films, and objects of a plurality of images.
The laser imager executes printing through assignment of an object ID, transfer of image of an object, and issuance of a print method (print command) and an object deletion method (indicated at 505).
For example, objects include an image object constituted of image data and its attributes, a film object constituted of a set of images and some film information, a session object constituted of a set of films and some session information, an LUT (look-up table) object, an overlay object, and other objects. The client requests the laser imager to construct each object and issues a method (command) for the object with a specific ID assigned thereto. In this manner, printing is executed.
After printing, unnecessary objects in the laser imager are deleted upon reception of a destruct method.
Thereafter, the laser imager notifies the client of a completion of destruction of objects. Upon reception of this notice, the client is released from the printing work.
As shown in FIGS. 20A and 20B during the operation by the laser imager 504, the client (e.g., CT 501) executes a series of sequences including requesting (513, 515, 516) the laser imager to construct one film object and two image objects for the film object, setting (514, 517, 518) information to the objects, issuing a print method 519, and thereafter issuing destruct methods 522, 523, and 524.
The print operation requires a relatively long time. Therefore, if a destruct command is issued before the print operation is not completed, the laser imager 504 rejects the destruct command (520, 521). In this case, the client 501 waits until the laser imager 504 completes the print operation, and there after issues the destruct commands 522, 523, and 524 to delete the objects (this is called hereinafter a first scheme). Alternatively, the laser imager loads a set of objects to be used for the print operation into a print queue (a first-in first-out unit for use with the print operation), and destructs the set of objects after the print operation to thereby neglect the destruct commands from the client 501 (this is called hereinafter a second scheme).
However, in the print operation at the object-oriented image drawing apparatus, typically a laser imager, the wait time of the client becomes long in the case of the first scheme, because the print operation takes a relatively long time and so the destruct command is rejected by the image drawing apparatus. The work efficiency of the client is therefore lowered greatly.
With the second scheme, if the client requests an additional print operation for the image objects, this print operation cannot be executed because the image drawing apparatus has deleted the image objects.